evening, where the headlines this sunday were all about princess diana and this new conspiracy theory about the crash that took her life. Scotland yard now looking into it, as we learn here more about where this latest theory came from. Abc's nick schifrin, again from london tonight. Reporter: It's the conspiracy theory that won't die. Princess diana and boyfriend dodi fayed killed not because of the paparazzi or a drunk driver, but because someone wanted them dead. Tonight, police investigating a new claim that diana was murdered by british special forces. The allegation source? A former soldier's estranged in-laws who just recently called police. Whenever you bring in stories about special forces, personnel, then immediately you've got the prospect of a red hot story. And there's a little bit of a conspiracy theorist in all of us, probably. Reporter: All the conspiracies were debunked by three investigations, but that's never stopped the critics, including fayed's dad. It's all made up as a cover-up, 100%. Reporter: But come on. She died 16 years ago. There's been no evidence of any cover-up. Can't we just put this to rest? Not so fast, says diana's former private secretary. The world should still care about diana, because her death leaves an unfillable gap. Reporter: She was the princess who braved mine fields. Just this week, prince harry visited angola in his mother's footsteps. For years, he'd carried and her legacy. All of us still fascinated by how she live and how she died. Nick schifrin, abc news, london.

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